Experimental study of a novel long pulse-width plasma ignition system to expand lean ignition limit of kerosene air mixture
image: The ignition process is defined as five stages: stage I represents the kernel generation stage, stage II represents the kernel propagation stage, stage III represents the flame residence stage, stage IV represents the flame growth stage, and stage V represents the stable combustion stage. The entire ignition process for the SI system consists of all of the five stages. The prolonged kernel duration, the larger energy, and the high penetration depth enhanced the ignition process. The flame residence stage as observed in traditional SI systems cannot be found during the LPWPI ignition process. The simplified four-stage process includes kernel generation, kernel propagation, flame growth, and stable combustion stage; thus facilitating the easier achievement of ignition compared to the traditional SI system.
Credit: Chinese Journal of Aeronautics
A breakthrough study published in Chinese Journal of Aeronautics by researchers from APPL (Aerospace Power System and Plasma Technology Laboratory) Air Force Engineering University presents an innovative solution: the Long Pulse-Width Plasma Ignition (LPWPI) system. This technology pioneers a dual-phase discharge architecture—initiating with high-voltage pulse to establish plasma channels, then transitioning to sustained arc discharge to maintain plasma torches. This design achieves a 45-fold extension of discharge duration (2.03 ms), improves energy efficiency to a record 61.1%, and doubles spark penetration depth to 24.1 mm. Validated in a single-head swirl combustor, LPWPI expanded lean ignition limits by 22.7%-39.3%, peaking at 39.3% under 1 455 SLM airflow conditions.
High-speed images revealed profound mechanistic innovation: Conventional spark ignition process is defined into five stages with a 10-30 ms "flame residence " where thermal radiation drops below detection thresholds. However, the LPWPI ignition process is different,which only can be defined into four continuous stages (kernel generation→propagation→flame growth→stable combustion). Take ignition process at gas flow rate of 1 092 SLM (equivalence ratio is 0.845) as an example to illustrate. In the SI system, heat dissipation causes dimming of the kernel's brightness from 4.68 ms to 25.88 ms, resulting in it being barely visible. In contrast to the SI system, the LPWPI sustains a more extensive ignition area with both the spark kernel and the flame remaining visible throughout the ignition process.
The novel ignition system has great potential in engineering implications. LPWPI maintains 22.7% boundary extension under 2 548 SLM high-speed turbulence, demonstrating exceptional environmental adaptability. Compared with the gliding discharge igniter, the LPWPI can work without the need for additional drive gas. The simplicity is attractive in practical application. Moreover, the 61.1% energy efficiency paves the way for hydrogen and sustainable aviation fuel applications. The team is now validating the system in a swirl-stabilized combustor under high-altitude conditions. It is believed that the revolutionary ignition technology is poised to become the cornerstone of next-generation aerospace propulsion.
Original Source
Zengyan WU, Zhenjie SHANG, Zhibo ZHANG, Huimin SONG, Min JIA, Yi CHEN, Yun WU, Yinghong LI. Experimental study of a novel long pulse-width plasma ignition system to expand lean ignition limit of kerosene air mixture [J]. Chinese Journal of Aeronautics, 2025, https://doi.org/10.1016/j.cja.2025.103601.
About Chinese Journal of Aeronautics
Chinese Journal of Aeronautics (CJA) is an open access, peer-reviewed international journal covering all aspects of aerospace engineering, monthly published by Elsevier. The Journal reports the scientific and technological achievements and frontiers in aeronautic engineering and astronautic engineering, in both theory and practice. CJA is indexed in SCI (IF = 5.7, Q1), EI, IAA, AJ, CSA, Scopus.